Pen



FIG. 1 is a perspective view of a pen showing my new design;

FIG. 2 is a rear elevational view;

FIG. 3 is a top plan view;

FIG. 4 is a front elevational view;

FIG. 5 is a right end elevational view; and

FIG. 6 is a left end elevational view. 

The ornamental design for a pen, substantially as shown. 